Yolk Sac Tumor of the Liver: An Important Differential for Liver Mass with Elevated Serum Alpha-Fetoprotein in the Pediatric Population

<b>Introduction:</b> Yolk sac tumor (YST) is a malignant germ cell tumor with 10-15% arising in extragonadal sites. <b>Methods:</b> A search through our institution's database from January 01, 1990, to December 31, 2020, for "yolk sac tumor" or "endodermal sinus tumor" and "liver". <b>Results:</b> Our search yielded three cases. A 20-month-old girl with a liver mass and serum alpha-fetoprotein (AFP) level of 46558.0 ng/mL. The neoplasm was papillary with Schiller-Duval bodies. A 2-year-old boy with hepatic masses and adrenal mass with a serum AFP of 106,604.5 ng/mL. Numerous Schiller-Duval bodies were present. A 7-month-old girl with a liver mass, lung nodules, and retroperitoneal masses. Serum AFP was in the 800s ng/mL. Hepatoid and microcystic YST were mixed with hepatoblastoma (HBL). All three cases were positive for CAM5.2, SALL4, Glypican-3, beta-catenin, and AFP. <b>Conclusion:</b> Hepatic yolk sac tumor should be considered in the differential of a liver mass in pediatric patients with elevated AFP.